The method of the project is to examine the discharge of single neurons in the awake monkey's cerebellum during natural posture and movement. The aim is to discover how cerebellar discharge differs from that of other parts of the motor system, and thus what unique properties the cerebellum contributes to the synthesis of posture and movement. Experiments in the previous grant period showed that dentate nucleus may precede motor cortex and interpositus nucleus in changing activity prior to a prompt volitional movement. These timing experiments suggest a sequence of neural events along anatomical pathways in which each station may contribute a property to the evolving motor command. Experiments in the forthcoming period if granted will systematically dissociate various aspects of movement of the wrist - pattern and force of muscular activity, angle of the wrist joint, mental anticipation of the direction of the next movement, and duration of the movement - to see if the different stations in the anatomical and temporal sequential pathway are preferantly concerned with one variable as opposed to another. Dr. Gilbert will record from Purkinje cells in cerebellar cortex to test Marr's and his own theory that the Purkinje cell plays a specific role in the learning of movements - by the climbing fiber heterosynaptically reinforcing mossy fiber - granule cell inputs to the Purkinje cell.